The Proteases and Cancer Program has primarily been a basic science program that has successfully worked to integrate translational and preclinical research into the program during the past three years. The research efforts of this program have concentrated on four major questions: (1) how the tumor microenvironment, including tumor/host interactions, alters proteolysis and the impact of this on anti-protease therapies;(2) what are the mechanisms (gene to protein) that regulate activation and inhibition of proteases and how can these be used to develop more efficacious inhibitors or alternative anti-protease strategies for use in vivo;(3) how proteases and their endogenous inhibitors function in normal developmental and non-cancerous pathological processes with the goal of identifying new therapeutic targets;and (4) what are the critical proteases and their functions in cell death and differentiation, also with the goal of identifying new targets. Proteases of the five endopeptidase classes are currently under study in the Program or through inter-programmatic collaborations in the Cancer Center. In terms of protease inhibitors, program members are performing structure-function analyses on endogenous protease inhibitors (e.g., tissue inhibitors of matrix metalloproteinases, plasminogen activator inhibitor-1, maspin, and cystatins), designing and testing known and novel synthetic inhibitors for matrix metalloproteinases, cysteine (calpain and cathepsin) and aspartic proteases and exploring other interactions that may modulate protease-associated functions (e.g., galectin-3, HB-EGF, annexin II heterotetramer, caveolae). Translational research efforts are directed toward: 1) development of novel protease inhibitors as potential therapeutic agents, 2) determining whether interactions that may modulate protease-associated functions might serve as novel targets for therapeutic intervention, and 3) developing novel methods and probes for in vitro and in vivo imaging of protease activity. There are four collaborative subprograms to explore these research areas with considerable crossover and collaboration among the subprograms and other Programs.